Re: [RFC PATCH v2 09/10] OvmfPkg/QemuFwCfgLib: Add Secure Encrypted Virtualization (SEV) support

[Brijesh Singh <brijesh.ksingh@gmail.com>]

On Mon, Mar 27, 2017 at 5:19 AM, Laszlo Ersek <lersek@redhat.com> wrote:

> On 03/21/17 22:13, Brijesh Singh wrote:
> > The patch adds SEV support in QemuFwCfgLib. When SEV is enabled:
> >
> >  * Pei phase support IO-style operations. This is mainly because we need
> to
> >    use a bounce buffer inorder to support DMA operation. Allocate a
> memory
> >    for bounce buffer can get painful in Pei phase hence if we detect
> FWCfg DMA
> >    support then silently fallback to IO.
> >
> > * Dxe phase supports both IO and DMA style operations.
> > ---
> >  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c        |   73 +++++++++++++
> >  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf   |    2
> >  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c        |  112
> ++++++++++++++++++++
> >  .../Library/QemuFwCfgLib/QemuFwCfgLibInternal.h    |   38 +++++++
> >  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c        |   93
> +++++++++++++++++
> >  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf   |    2
> >  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c        |   82
> +++++++++++++++
> >  7 files changed, 402 insertions(+)
>
> Can you please split this patch into 5 patches?
> - new interfaces in QemuFwCfgLibInternal.h
> - implementation of new APIs for SEC instance
> - implementation of new APIs for PEI instance
> - implementation of new APIs for DXE instance
> - call new APIs from common code
>
> If that is possible. Otherwise, it's quite hard to review & compare the
> instances for the different firmware phases.
>
>
Sure I will divide into multiple patches.



> Anyway, some things I've noticed:
>
> - InternalQemuFwCfgSevIsEnabled() should use global variables in the PEI
> instance as well. Possibly the appropriate interface from
> BaseMemcryptSevLib could be called from both the PEI and DXE instances
> here. (I think the DXE instance already does that.)
>
>
Id tou are okay with it then I will perfer to use BaseMemEncryptSevLib's
provided function in both PEI and DXE phases.



> - regarding InternalQemuFwCfgDmaBytes(): would it be possible to hook
> the SEV-related tricks into the existent function, rather than
> copy+modify the entire function as InternalQemuFwCfgSevDmaBytes()? It
> seems to me that a conditional "prologue" and "epilogue" in
> InternalQemuFwCfgDmaBytes() could do the trick.
>
>
I wanted to reuse the existing function but I was not sure how do you
wanted me to handle static allocation of "Access" variable inside
the InternalQemuFwCfgDmaBytes()

 VOID
 InternalQemuFwCfgDmaBytes (
   IN     UINT32   Size,
   IN OUT VOID     *Buffer OPTIONAL,
   IN     UINT32   Control
   )
 {
   volatile FW_CFG_DMA_ACCESS Access;
   UINT32                     AccessHigh, AccessLow;
   UINT32                     Status;


The "Access" variable is statically allocated inside this function, in case
of SEV the Dma "Access" control variable need to be dynamically allocated
because hypervisor read/writes data into Access->status.

I could convert Access into FW_CFG_DMA_ACCESS pointer for non SEV case and
then integerate the SEV specific changes inside the same function.

I was just not sure which approach is prefrered hence decided to create a
new function for now and at least start the discussion.




> ... From skimming this patch, I think those are the only
> functionality-related comments I have at this point, beyond the remarks
> I made elsewhere in this series (like: line length, DEBUG_* macros, and
> so on). Please recheck all patches for those comments.
>
>
I will revist all the patches and fix those DEBUG_* macros.



> >
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> > index ac05f4c..be8e945 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> > @@ -4,6 +4,7 @@
> >
> >    Copyright (C) 2013, Red Hat, Inc.
> >    Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
> > +  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
> >
> >    This program and the accompanying materials are licensed and made
> available
> >    under the terms and conditions of the BSD License which accompanies
> this
> > @@ -14,14 +15,34 @@
> >    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> >  **/
> >
> > +#include "Uefi.h"
> > +
> > +#include <Library/BaseLib.h>
> >  #include <Library/DebugLib.h>
> >  #include <Library/QemuFwCfgLib.h>
> > +#include <Library/UefiBootServicesTableLib.h>
> > +#include <Library/MemEncryptSevLib.h>
> > +#include <Library/BmDmaLib.h>
> >
> >  #include "QemuFwCfgLibInternal.h"
> >
> >  STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
> >  STATIC BOOLEAN mQemuFwCfgDmaSupported;
> > +STATIC BOOLEAN mQemuFwCfgSevIsEnabled = FALSE;
> > +
> > +/**
> > + Returns a boolean indicating whether the SEV is enabled
> >
> > + @retval    TRUE    SEV is enabled
> > + @retval    FALSE   SEV is not enabled
> > +**/
> > +BOOLEAN
> > +InternalQemuFwCfgSevIsEnabled (
> > +  VOID
> > +  )
> > +{
> > +  return mQemuFwCfgSevIsEnabled;
> > +}
> >
> >  /**
> >    Returns a boolean indicating if the firmware configuration interface
> > @@ -79,6 +100,9 @@ QemuFwCfgInitialize (
> >      mQemuFwCfgDmaSupported = TRUE;
> >      DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
> >    }
> > +
> > +  mQemuFwCfgSevIsEnabled = MemEncryptSevIsEnabled ();
> > +
> >    return RETURN_SUCCESS;
> >  }
> >
> > @@ -114,3 +138,52 @@ InternalQemuFwCfgDmaIsAvailable (
> >  {
> >    return mQemuFwCfgDmaSupported;
> >  }
> > +
> > +/**
> > + Allocate a bounce buffer for SEV DMA.
> > +
>
> Please document that this function either succeeds or doesn't return.
>
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[out]    Buffer   Allocated DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaAllocateBuffer (
> > +  IN     UINT32   NumPages,
> > +  OUT    VOID     **Buffer
> > +  )
> > +{
> > +  EFI_STATUS  Status;
> > +
> > +  //
> > +  // Allocate DMA bounce buffer
> > +  //
> > +  Status = BmDmaAllocateBuffer (TRUE, EfiBootServicesData, NumPages,
> Buffer);
> > +  if (EFI_ERROR(Status)) {
> > +    DEBUG ((EFI_D_ERROR, "SEV: Failed to allocate bounce buffer %d
> pages\n", NumPages));
> > +    ASSERT_EFI_ERROR (Status);
> > +    CpuDeadLoop ();
> > +  }
> > +
> > +  DEBUG ((EFI_D_VERBOSE, "QemuFwCfgSevDma allocate buffer 0x%Lx Pages
> %d\n", (UINTN)Buffer, NumPages));
> > +}
> > +
> > +/**
> > + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
> eBuffer
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[in]     Buffer   DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaFreeBuffer (
> > +  IN     VOID     *Buffer,
> > +  IN     UINT32   NumPages
> > +  )
> > +{
> > +  //
> > +  // Free the bounce buffer
> > +  //
> > +  DEBUG ((EFI_D_VERBOSE, "QemuFwCfgSevDma free buffer 0x%Lx Pages
> %d\n", (UINTN)Buffer, NumPages));
> > +  BmDmaFreeBuffer (Buffer, NumPages);
> > +}
> > +
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> > index 346bb88..536887f 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> > @@ -47,4 +47,6 @@
> >    DebugLib
> >    IoLib
> >    MemoryAllocationLib
> > +  MemEncryptSevLib
> > +  BmDmaLib
> >
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
> > index 1bf725d..d2560a3 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
> > @@ -47,6 +47,111 @@ QemuFwCfgSelectItem (
> >
> >
> >  /**
> > +  Transfer an array of bytes, or skip a number of bytes, using the SEV
> DMA bounce
> > +  interface. The function is same as InternalQemuFwCfgDmaBytes with
> excpetion that
> > +  it uses bounce buffer
> > +
> > +  @param[in]     Size     Size in bytes to transfer or skip.
> > +
> > +  @param[in,out] HostBuffer Buffer to read data into or write data
> from. Ignored,
> > +                            and may be NULL, if Size is zero, or
> Control is
> > +                            FW_CFG_DMA_CTL_SKIP.
> > +
> > +  @param[in]     Control  One of the following:
> > +                          FW_CFG_DMA_CTL_WRITE - write to fw_cfg from
> Buffer.
> > +                          FW_CFG_DMA_CTL_READ  - read from fw_cfg into
> Buffer.
> > +                          FW_CFG_DMA_CTL_SKIP  - skip bytes in fw_cfg.
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaBytes (
> > +  IN     UINT32   Size,
> > +  IN OUT VOID     *HostBuffer OPTIONAL,
> > +  IN     UINT32   Control
> > +  )
> > +{
> > +  volatile FW_CFG_DMA_ACCESS *Access;
> > +  UINT32                     AccessHigh, AccessLow;
> > +  UINT32                     Status;
> > +  UINT32                     NumPages;
> > +  VOID                       *DmaBuffer, *Buffer;
> > +
> > +  //
> > +  // Calculate number of pages we need to allocate for this operation
> > +  //
> > +  if (Control == FW_CFG_DMA_CTL_SKIP) {
> > +    //
> > +    // Control data does not need the actual buffer
> > +    //
> > +    NumPages = EFI_SIZE_TO_PAGES (sizeof (*Access));
> > +  } else {
> > +    NumPages = EFI_SIZE_TO_PAGES (sizeof (*Access) + Size);
> > +  }
> > +
> > +  //
> > +  // Allocate DMA bounce buffer
> > +  //
> > +  InternalQemuFwCfgSevDmaAllocateBuffer (NumPages, &DmaBuffer);
> > +
> > +  Access = (FW_CFG_DMA_ACCESS *)DmaBuffer;
> > +  Buffer = DmaBuffer + sizeof(*Access);
> > +
> > +  Access->Control = SwapBytes32 (Control);
> > +  Access->Length  = SwapBytes32 (Size);
> > +  Access->Address = SwapBytes64 ((UINTN)Buffer);
> > +
> > +  //
> > +  // Copy data from Host buffer into DMA buffer
> > +  //
> > +  if (HostBuffer && (Control == FW_CFG_DMA_CTL_WRITE)) {
> > +    CopyMem (Buffer, HostBuffer, Size);
> > +  }
> > +
> > +  //
> > +  // Delimit the transfer from (a) modifications to Access, (b) in case
> of a
> > +  // write, from writes to Buffer by the caller.
> > +  //
> > +  MemoryFence ();
> > +
> > +  //
> > +  // Start the transfer.
> > +  //
> > +  AccessHigh = (UINT32)RShiftU64 ((UINTN)Access, 32);
> > +  AccessLow  = (UINT32)(UINTN)Access;
> > +  IoWrite32 (FW_CFG_IO_DMA_ADDRESS,     SwapBytes32 (AccessHigh));
> > +  IoWrite32 (FW_CFG_IO_DMA_ADDRESS + 4, SwapBytes32 (AccessLow));
> > +
> > +  //
> > +  // Don't look at Access->Control before starting the transfer.
> > +  //
> > +  MemoryFence ();
> > +
> > +  //
> > +  // Wait for the transfer to complete.
> > +  //
> > +  do {
> > +    Status = SwapBytes32 (Access->Control);
> > +    ASSERT ((Status & FW_CFG_DMA_CTL_ERROR) == 0);
> > +  } while (Status != 0);
> > +
> > +  //
> > +  // After a read, the caller will want to use Buffer.
> > +  //
> > +  MemoryFence ();
> > +
> > +  //
> > +  // Copy data from DMA buffer into Host Buffer
> > +  //
> > +  if (HostBuffer && (Control == FW_CFG_DMA_CTL_READ)) {
> > +    CopyMem (HostBuffer, Buffer, Size);
> > +  }
> > +
> > +  //
> > +  // Free the DMA bounce buffer
> > +  //
> > +  InternalQemuFwCfgSevDmaFreeBuffer (DmaBuffer, NumPages);
> > +}
> > +
> > +/**
> >    Transfer an array of bytes, or skip a number of bytes, using the DMA
> >    interface.
> >
> > @@ -79,6 +184,13 @@ InternalQemuFwCfgDmaBytes (
> >      return;
> >    }
> >
> > +  //
> > +  // When SEV is enabled then use SEV version of DmaReadWrite
> > +  //
> > +  if (InternalQemuFwCfgSevIsEnabled ()) {
> > +    return InternalQemuFwCfgSevDmaBytes (Size, Buffer, Control);
> > +  }
> > +
> >    Access.Control = SwapBytes32 (Control);
> >    Access.Length  = SwapBytes32 (Size);
> >    Access.Address = SwapBytes64 ((UINTN)Buffer);
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
> > index 6e87c62..8e2ff45 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
> > @@ -2,6 +2,7 @@
> >    Internal interfaces specific to the QemuFwCfgLib instances in OvmfPkg.
> >
> >    Copyright (C) 2016, Red Hat, Inc.
> > +  Copyright (C) 2017, Advanced Micro Devices.
> >
> >    This program and the accompanying materials are licensed and made
> available
> >    under the terms and conditions of the BSD License which accompanies
> this
> > @@ -43,4 +44,41 @@ InternalQemuFwCfgDmaIsAvailable (
> >    VOID
> >    );
> >
> > +/**
> > + Returns a boolean indicating whether the SEV is enabled
> > +
> > + @retval    TRUE    SEV is enabled
> > + @retval    FALSE   SEV is not enabled
> > +**/
> > +BOOLEAN
> > +InternalQemuFwCfgSevIsEnabled (
> > +  VOID
> > +  );
> > +
> > +/**
> > + Allocate a bounce buffer for SEV DMA.
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[out]    Buffer   Allocated DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaAllocateBuffer (
> > +  IN     UINT32   NumPages,
> > +  OUT    VOID     **Buffer
> > +  );
> > +
> > +/**
> > + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
> eBuffer
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[in]     Buffer   DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaFreeBuffer (
> > +  IN     VOID     *Buffer,
> > +  IN     UINT32   NumPages
> > +  );
> > +
> >  #endif
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> > index ac05f4c..3dc9270 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> > @@ -4,6 +4,7 @@
> >
> >    Copyright (C) 2013, Red Hat, Inc.
> >    Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
> > +  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
> >
> >    This program and the accompanying materials are licensed and made
> available
> >    under the terms and conditions of the BSD License which accompanies
> this
> > @@ -14,14 +15,55 @@
> >    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> >  **/
> >
> > +#include <Library/BaseLib.h>
> >  #include <Library/DebugLib.h>
> >  #include <Library/QemuFwCfgLib.h>
> > +#include <Register/Cpuid.h>
> > +#include <Register/AmdSevMap.h>
> >
> >  #include "QemuFwCfgLibInternal.h"
> >
> >  STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
> >  STATIC BOOLEAN mQemuFwCfgDmaSupported;
> >
> > +/**
> > + Returns a boolean indicating whether the SEV is enabled
> > +
> > + @retval    TRUE    SEV is enabled
> > + @retval    FALSE   SEV is not enabled
> > +**/
> > +BOOLEAN
> > +InternalQemuFwCfgSevIsEnabled (
> > +  VOID
> > +  )
> > +{
> > +  UINT32 RegEax;
> > +  MSR_SEV_STATUS_REGISTER Msr;
> > +  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
> > +
> > +  //
> > +  // Check if memory encryption leaf exist
> > +  //
> > +  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
> > +  if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
> > +    //
> > +    // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
> > +    //
> > +    AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL,
> NULL);
> > +
> > +    if (Eax.Bits.SevBit) {
> > +      //
> > +      // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
> > +      //
> > +      Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
> > +      if (Msr.Bits.SevBit) {
> > +        return TRUE;
> > +      }
> > +    }
> > +  }
> > +
> > +  return FALSE;
> > +}
> >
> >  /**
> >    Returns a boolean indicating if the firmware configuration interface
> > @@ -79,6 +121,17 @@ QemuFwCfgInitialize (
> >      mQemuFwCfgDmaSupported = TRUE;
> >      DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
> >    }
> > +
> > +  //
> > +  // When SEV is enabled then we do not support DMA interface.
> > +  // This is because we need to use bounce buffer to support DMA
> operation in SEV guest.
> > +  // Allocating memory for bounce buffer can get painful in Pei phase
> > +  //
> > +  if (mQemuFwCfgDmaSupported && InternalQemuFwCfgSevIsEnabled ()) {
> > +    mQemuFwCfgDmaSupported = FALSE;
> > +    DEBUG ((DEBUG_INFO, "QemuFwCfg disabling DMA interface and
> defaulting to IO Port.\n"));
> > +  }
> > +
> >    return RETURN_SUCCESS;
> >  }
> >
> > @@ -114,3 +167,43 @@ InternalQemuFwCfgDmaIsAvailable (
> >  {
> >    return mQemuFwCfgDmaSupported;
> >  }
> > +
> > +/**
> > + Allocate a bounce buffer for SEV DMA.
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[out]    Buffer   Allocated DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaAllocateBuffer (
> > +  IN     UINT32   NumPages,
> > +  OUT    VOID     **Buffer
> > +  )
> > +{
> > +  //
> > +  // We should never reach here
> > +  //
> > +  ASSERT (FALSE);
> > +  CpuDeadLoop ();
> > +}
> > +
> > +/**
> > + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
> eBuffer
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[in]     Buffer   DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaFreeBuffer (
> > +  IN     VOID     *Buffer,
> > +  IN     UINT32   NumPages
> > +  )
> > +{
> > +  //
> > +  // We should never reach here
> > +  //
> > +  ASSERT (FALSE);
> > +  CpuDeadLoop ();
> > +}
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> > index 4f966a8..83cc0de 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> > @@ -39,7 +39,9 @@
> >
> >  [Packages]
> >    MdePkg/MdePkg.dec
> > +  MdeModulePkg/MdeModulePkg.dec
> >    OvmfPkg/OvmfPkg.dec
> > +  UefiCpuPkg/UefiCpuPkg.dec
> >
> >  [LibraryClasses]
> >    BaseLib
> > diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
> > index 465ccbe..70b0a47 100644
> > --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
> > +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
> > @@ -16,8 +16,11 @@
> >    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> >  **/
> >
> > +#include <Library/BaseLib.h>
> >  #include <Library/DebugLib.h>
> >  #include <Library/QemuFwCfgLib.h>
> > +#include <Register/Cpuid.h>
> > +#include <Register/AmdSevMap.h>
> >
> >  #include "QemuFwCfgLibInternal.h"
> >
> > @@ -94,3 +97,82 @@ InternalQemuFwCfgDmaIsAvailable (
> >  {
> >    return FALSE;
> >  }
> > +
> > +/**
> > + Returns a boolean indicating whether the SEV is enabled
> > +
> > + @retval    TRUE    SEV is enabled
> > + @retval    FALSE   SEV is not enabled
> > +**/
> > +BOOLEAN
> > +InternalQemuFwCfgSevIsEnabled (
> > +  VOID
> > +  )
> > +{
> > +  UINT32 RegEax;
> > +  MSR_SEV_STATUS_REGISTER Msr;
> > +  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
> > +
> > +  //
> > +  // Check if memory encryption leaf exist
> > +  //
> > +  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
> > +  if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
> > +    //
> > +    // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
> > +    //
> > +    AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL,
> NULL);
> > +
> > +    if (Eax.Bits.SevBit) {
> > +      //
> > +      // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
> > +      //
> > +      Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
> > +      if (Msr.Bits.SevBit) {
> > +        return TRUE;
> > +      }
> > +    }
> > +  }
> > +
> > +  return FALSE;
> > +}
> > +
> > +/**
> > + Allocate a bounce buffer for SEV DMA.
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[out]    Buffer   Allocated DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaAllocateBuffer (
> > +  IN     UINT32   NumPages,
> > +  OUT    VOID     **Buffer
> > +  )
> > +{
> > +  //
> > +  // We should never reach here
> > +  //
> > +  ASSERT (FALSE);
> > +  CpuDeadLoop ();
> > +}
> > +
> > +/**
> > + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
> eBuffer
> > +
> > +  @param[in]     NumPage  Number of pages.
> > +  @param[in]     Buffer   DMA Buffer pointer
> > +
> > +**/
> > +VOID
> > +InternalQemuFwCfgSevDmaFreeBuffer (
> > +  IN     VOID     *Buffer,
> > +  IN     UINT32   NumPages
> > +  )
> > +{
> > +  //
> > +  // We should never reach here
> > +  //
> > +  ASSERT (FALSE);
> > +  CpuDeadLoop ();
> > +}
> >
> > _______________________________________________
> > edk2-devel mailing list
> > edk2-devel@lists.01.org
> > https://lists.01.org/mailman/listinfo/edk2-devel
> >
>
>


-- 
Confusion is always the most honest response.